The present invention relates broadly to a chassis member for carrying at least one circuit board, and to a WDM multiplexer module. The present invention also relates to an optical network node and to an optical network.
Optical networks may be classified into long haul optical networks, metro optical networks, access optical networks and enterprise gear-optical networks. Distinctions between the different types may in a first instance be drawn on the basis of physical transmission distances covered, decreasing from long haul optical networks down to enterprise gear-optical networks, with the latter being typically implemented within one location e.g. in one office building.
The different types of optical networks can also be distinguished in terms of the physical environment in which in particular add/drop equipment is located. For example, for enterprise gear-optical networks, the add/drop equipment is typically located inside of air conditioned buildings, and therefore no particular extreme temperature condition compliance is required to implement such optical networks. For long haul and metro optical networks, which typically involve very complex and expensive equipment, add/drop equipment is typically located in telecommunications carriers central offices and points of presence and are subjected to a limited range of temperatures, which is sometimes referred to as requiring the add/drop equipment to be carrier class compliant. This temperature range is typically in the range of xe2x88x925 to 55xc2x0 C. as required for Telcordia NEBS level 3.
However, in access optical networks the add/drop equipment is typically located in an outside plant (OSP) situation, and thus potentially subjected to a wider temperature range than e.g. carrier class compliance requirements.
Currently, the only optical networks that can be implemented in scenarios where the required add/drop equipment is located in an OSP situation are Time Domain Multiplexing (TDM) based networks. So far, WDM based optical networks have not been deemed suitable for implementation in OSP situations, as currently available WDM equipment is not OSP compatible. However, it would be desirable to implement WDM based optical networks in such an environment, to utilise the larger capacity in the optical domain in access optical networks. It would further be desirable if such an implementation could be achieved in a compact design for the hardware involved.
At least preferred embodiments of the present invention seek to provide a chassis member for carrying at least one circuit board, or a WDM multiplexer module suitable for use in an OSP situation and facilitating a compact hardware design.
In accordance with a first aspect of the present invention there is provided a chassis member for carrying at least one circuit board for use in aWDM add/drop multiplexer unit, wherein the chassis member is adapted, in use, to function as a heatsink for a heat generating component mounted on the circuit board.
In one embodiment, a main body of the chassis is contoured or shaped in a manner such that, in use, a distance between the heat generating component and a region of the main body facing the heat generating component is reduced compared to other components on the circuit board.
The chassis member may comprise sidewalls formed around the peripheral region of the main body and adapted to function, in use, as at least a portion of housing sidewalls of a housing structure for the circuit board.
The chassis member may be adapted, in use, to carry at least one circuit board above and at least one circuit board below of the main body.
In one embodiment, the chassis member comprises one or more highly thermally conductive members for facilitating the heatsink functionality.
The one or more highly thermally conductive members may be in the form of heat pipes containing a working fluid.
The working fluid may be water.
The heat pipe may be mounted on a surface of the chassis element or embedded in the chassis element.
In one embodiment, the chassis is formed from two or more pieces and one or more of the pieces comprises one or more capillary members, wherein when the chassis member is assembled the capillary members can function as the highly thermally conductive members
The chassis member may comprise a malleable thermal pad element disposed such that, when the chassis member is inserted into a mounting unit for mounting, the thermal pad abuts a heatsink structure of the mounting unit for operation, whereby a relative movement between the chassis member and the heatsink structure caused by different thermal expansion coefficients is accommodated over a temperature range.
The chassis member may be arranged, in use, such that the thermal connection to the heatsink structure is poorer at lower temperatures compared to higher temperatures. One or more of the group comprising the thermal pad, the heatsink structure and the chassis member may be arranged, in use, to effect the poorer thermal connection at lower temperatures.
Loss of contact may occur, in use, between the heat sink structure and the thermal pad below a threshold temperature.
In one embodiment, the chassis member further comprises a locking element for locking the chassis member into position when inserted in a mounting for operation unit.
The locking element may be arranged such that the chassis member is biased when inserted into position in the mounting unit, whereby a thermal connection between the chassis member and a heatsink structure of the rack unit is maintained over a temperature range by accommodating relative movement between the chassis member and the heatsink structure caused by different thermal expansion coefficients.
In accordance with a second aspect of the present invention there is provided a WDM multiplexer module comprising:
a housing,
a chassis member located substantially inside the housing and adapted to function as a heat sink,
a heat sink structure extending from the housing and in thermal communication with the chassis member,
a thermoelectric (TE) device in thermal communication with the chassis member,
at least one heat generating electrical component in thermal communication with the chassis member, and
a control unit arranged, in use, to maintain a controlled temperature environment inside the housing utilising the heat sink structure, the TE device, and the heat generating electrical component and utilising the chassis member as a thermal communication medium.
The module may further comprise one or more highly thermally conductive members formed in or on the chassis member to facilitate the heatsink functionality of the chassis member.
In one embodiment, the module further comprises a local thermal environment structure located inside the housing and the TE device is in thermal communication with the chassis member and the local thermal environment structure,
whereby, in use, a second stage controlled temperature environment is created substantially inside the local thermal environment structure, and
wherein temperature variations in the second stage controlled temperature environment are smaller than temperature variations inside the housing.
The module may comprise at least one laser source disposed in a manner such that, in use, the source temperature of the laser source is substantially governed by the second stage controlled temperature environment.
In one embodiment, the laser source is a semiconductor laser source, and a junction of the laser source is located substantially inside the local thermal environment structure.
A laser driver associated with the laser source may be located substantially outside the local thermal environment structure, whereby the thermal environment around the laser driver is governed by the controlled temperature environment inside the housing.
The module may comprise a plurality of electrical components, and the control unit is further arranged, in use during start-up or re-start of the module, to sequentially switch on the electrical components based on operating temperature specifications and heat generating characteristics of the electrical components to facilitate creation of the controlled temperature environment.
The heat sink structure may comprise at least one heat pipe.
The heat pipe may have a working fluid characterised by a freezing temperature above xe2x88x9240xc2x0 C., whereby a discontinuity in heat transfer to and from the heat sink structure is created for temperatures below the freezing temperature of the working fluid in the heat pipe for reducing heat loss from the inside of the housing. The freezing temperature may be about zero xc2x0 C.
In one embodiment, the chassis member comprises side walls formed around the peripheral region of a main body of the chassis member, and said side walls form at least a portion of housing side walls of the housing.
The housing may be adapted to function as an electromagnetic induction (EMI) shield.
The module may further comprise biasing means for biasing the chassis member with respect to the heatsink structure.
In one embodiment, the module further comprises a first key member arranged, in use, to cooperate with a second key member formed on a casing member into which the module is inserted, to prevent the module from making contact with a backplane of the casing member when the module is inserted with a correct orientation into a slot of the casing member for which the module is not intended.